MIL moved a block away

Hey guys, so I’m new here but I just really need advice and wasn’t sure where to go. My husband and I (w/ two kids) just bought our first house in an adorable area in a great school district. We were soooo exited about renovating, moving in, living 15 feet away from a park, being walking distance from, the elementary school, and all the things new home owners are exited about. Well about two weeks ago we closed on the property (so it’s too late to do anything now) and today we just found out my MIL put an offer in on a house and it was ACCEPTED. She’s about a 7min walk from us in a small neighborhood one entrance/ exit, one park etc. I’m so angry and sad. We tried talking to her and telling her how we feel but she ultimately said she won’t be a bother to us and doesn’t care what we say. Am i being dramatic for being so angry i literally want to cut contact? This feel like such an over step i cant even bare it.
What do I do?!?!? I have a letter drafted to go to the current owners🫣 but idk if that’s too far.

Side notes: she pretty much abandoned my husband and his siblings and moved across the country to marry some guy so MIL and my husband have a strange more friend like relationship. She tends to be quite pushy and can be super manipulative so this feels like a way for her to try and muscle her way into our lives but she says it’s for financial gain since it’ll go up in value OR so that maybe one day her daughter (husbands sister) can buy it off them and their child can go to those great schools. (Which is The two points directly contradict each other since she’d be selling it to my husband’s sister for cheap seeing as they could not afford at market value.

Things I’m worried about are she shows up at my door randomly, she asks to babysit my kids (k don’t trust someone who left her 3 year old for a man to watch my kids), (she has some obsession with MY family my mom and grandparents) every time she sees their cars she’s gonna want to stop by, we have a beautiful club house pool that I don’t want her inviting all the family members over to because we’re there and what fun would it be to have everyone over to the pool )my husbands family is full of narcissistic A**holes and talk crap about EVERYONES appearance). Truthfully I want to swim in peace with my kids with my bloat and leg stubble without worrying about them judging me!!! And I want to get my mail in a messy bun and pajamas at 4pm (SAHM) without her driving by!